The present invention relates to a device manufacturing apparatus used in the manufacture of microdevices, e.g., a semiconductor chip such as an IC or LSI, a liquid crystal panel, a CCD, a thin film magnetic head, and a micromachine, and more particularly, to a correcting method of correcting a change in optical characteristics of a projection optical system in the device manufacturing apparatus.
In recent years, demand for a further reduction in feature size and a higher integration degree have arisen for semiconductor elements, LSIs, and VLSIs, and accordingly an image forming (projection) optical system with a high resolution is required in a projection exposure apparatus. Therefore, the NA of the image forming optical system is increasing, while the depth of focus of the image forming optical system is decreasing.
In a projection exposure apparatus of this type, the focal position (image surface position) and magnification of its projection optical system change due to a change in atmospheric pressure of the projection optical system, a temperature increase caused by light beams irradiated on the projection optical system, a temperature increase caused by heat generated by the apparatus including the projection optical system, and the like. These changes in focal position and magnification must be corrected.
A correction method is described in, e.g., Japanese Patent Laid-Open No. 10-41226 (xe2x80x9cProjection Optical Apparatus and Method of Adjusting Image Forming Characteristicxe2x80x9d). In this reference, in order to correct a change in a projection optical system upon a temperature increase caused by irradiated light beams, a change in focal position of the projection optical system and a change in magnification of the projection optical system, which are caused by a temperature change, are calculated based on a model formula, and are corrected. The state of focus after correction is detected by a focus detection mechanism. If a good in-focus state is not obtained, further correction control is performed. Fluctuation in magnification is also corrected in the same manner as in correction of the change in focal position.
As described above, conventionally, in order to correct a change in a projection optical system upon a temperature increase caused by incoming light beams, a change in focal position of the projection optical system and a change in magnification of the projection optical system, which are caused by a temperature change, are calculated based on a model formula, and are corrected. The state of focus after correction is detected by a focus detection mechanism. If a good in-focus state is not obtained, further focal position correction control is performed.
If the magnification fluctuates, it is corrected by calculating a correction amount with a model formula in the same manner as in the correction of the change in focal position. The state of magnification after correction is detected by a magnification detection mechanism. If a good magnification is not obtained, further magnification correction control is performed.
When detecting the state of focus with the focus detection mechanism and the magnification with the magnification detection mechanism, it takes time to process the detection results, thereby degrading the throughput in the manufacture of semiconductor devices.
The present invention has been made in consideration of the problems of the prior art described above, and has as its object to improve the throughput in the manufacture of semiconductor chips, liquid crystal panels, and the like.
In order to achieve the above object, according to the present invention, there is provided an exposure apparatus for projecting a master pattern onto a substrate with a projection optical system, having detection means for obtaining fluctuation information of at least one optical characteristic of the projection optical system, first arithmetic operation means for obtaining an adjustment amount of at least one optical characteristic on the basis of the fluctuation information, and second arithmetic operation means for calculating fluctuation information of the other optical characteristics in accordance with the obtained fluctuation information. According to the present invention, there is also provided a device manufacturing apparatus characterized by comprising data acquiring means for acquiring fluctuation information of optical characteristics of a projection optical system in the apparatus, adjusting means for adjusting the optical characteristics of the projection optical system, and arithmetic operation means for calculating an adjustment amount, to be instructed to the adjusting means, on the basis of a change characteristic model formula of the optical characteristics and data obtained by the data acquiring means, the data acquiring means detecting at least a small part of not less than two types of fluctuation information, and the arithmetic operation means calculating the other fluctuation information from a detection result of the small part of fluctuation information.
In order to calculate the other fluctuation information, the arithmetic operation means may comprise data storage means for storing in the form of data a relationship between the small part of the fluctuation information and the other fluctuation information, and fluctuation information extracting means for extracting the other fluctuation information stored in advance from the data storage means on the basis of a detection result of the fluctuation information obtained by the data acquiring means. At least two types of fluctuation information include focus information and magnification information of the projection optical system. In this case, one of the focus information and fluctuation information may be detected, while the other one is obtained by an arithmetic operation or looking up in a table.
According to the present invention, when measuring fluctuation in optical characteristics and calibrating at least two types of fluctuation information calculated by using the model formula, only a small part of the fluctuation information is actually measured while the other fluctuation information is obtained by calculation on the basis of the actual measurement value or by looking up in a table. Thus, a time-consuming process such as measurement of a focal position or magnification can be omitted, so that the throughput in the device manufacture can be improved. In particular, if the fluctuation information is on, e.g., fluctuation in focal position and fluctuation in magnification that have a high correlation with each other, if one data is actually measured, the other data can be obtained at high precision by an arithmetic operation or by looking up in a table. Accordingly, correction, which is by no means inferior to correction performed by actually measuring the two pieces of data, can be performed.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.